COMP 3513 - Assignment #7 --- Entity-Relationship Diagrams
- Solution
Page 312-313
3. Transform the E-R diagram of Figure 9–21 into a set of 3NF relations.
Listed below are 3NF relations for the E–R diagram. Foreign keys are shown with
a dashed underline. QUOTE QUANTITY is not sufficient as the primary key of the
PRICEQUOTE relation, but this attribute along with the primary keys of the two
associated entities is a sufficient concatenated (or composite) primary key for this
associative entity. The PART RECEIPT entity is called a weak or attributive
entity, since its existence depends on a PRICE QUOTE entity instance. In this
case, however, the PART RECEIPT entity has its own primary key, ORDER NO.
The 3NF relations are:
VENDOR (Vendor No, Address)
PRICEQUOTE (Vendor No, Item No, Quote Quantity, Price)
PART (Item No, Desc)
PART RECEIPT (Order No, Vendor No, Item No, Quote Quantity, Date,
Order_Quantity)